National Health and Nutrition Examination Survey

The Mobile Examination Center (MEC) interview section on sexual behavior (variable name prefix SXQ) provides information on lifetime and current sexual behavior for both males and females. Major items in this section include age at first sexual intercourse, number of sexual partners, circumcision status (males), and history of sexually transmitted diseases.

Survey participants aged 14-69 years were eligible. Several questions in this section are age and gender-specific. Mentally impaired individuals, or participants who were unable to understand English or Spanish were not asked these questions. Only data from participants aged 14-17 years old are included in this Research Data Center (RDC) file. The data files for participants 18-69 years old are publicly available through the NHANES website.

The sexual behavior questionnaire was self-administered in a private room in the MEC, during the MEC Interview, using the Audio Computer Assisted Self Interview (ACASI) system. The ACASI was conducted in either English or Spanish. The ACASI enables respondents to hear questions through earphones as well as read questions on the computer screen. Respondents move at their own speed and touch the screen to indicate their response. No proxy respondents or translators were used in situations when the respondents could not self-report. The questionnaire is located on the NHANES website at: https://wwwn.cdc.gov/nchs/data/nhanes/2015-2016/questionnaires/sxq_acasi_i.pdf.

For details on the QA/QC process for this component, please refer to the MEC Interview Manual on the NHANES website.

Please see Appendix 1 (for male) and Appendix 2 (for female) for detailed information on variables included in the SXQ section in the latest seven release cycles.

The sexual behavior questionnaire in 2015-2016 is the same as in 2013-2014, 2011-2012 and 2009-2010, with the exception of some very slight exceptions. For example, beginning in 2013, NHANES started asking participants who answered yes to having been told by a doctor or other health care professional that they had genital warts, how old they were when they were first told that they had genital warts.. Analysts should be cautious when combining data with cycles prior to the NHANES 2009-2010 SXQ data, since some questions have been removed or added, and some questions have had slight wording changes.

The variable SXD021 (Ever had vaginal, anal, or oral sex) was derived from whether or not the respondent had reported having any of the specific types of sex. For example, if a male answered “yes” to having had any of the following types of sex: SXQ800 (Ever had vaginal sex with a woman), SXQ803 (Ever performed oral sex on a woman), SXQ806 (Ever had anal sex with a woman), or SXQ809 (Ever had any sex with a man; anal, oral); he would be coded as a “1” or “yes” in SXD021.

Responses to SXD031 (age at first sexual intercourse), SXD633 (age first performed oral sex on a woman), and SXD621 (age when first had oral sex) that were 9 years or less were grouped and coded as “9 years or younger.”

Information was collected using two-part (number and unit) questions for both SXD630 (last performed oral sex on a new male partner) and SXD642 (last performed oral sex on a new female partner). This is to allow participants to report how long ago they had performed oral sex either in days, weeks, months, or years. The released variables were edited to standardize the reported length of time to number of days, using the following conversion factors: 7 days per week, 30.4 days per month, and 365.25 days per year.

In general, if a person wasn't asked a question, the response to the question is shown as “missing.” It is up to the analysts to recode the response to zero as they see fit. For example, if a respondent reported that they had zero lifetime vaginal sex partners, they wouldn't be asked the number of vaginal sex partners in the past 12 months. Since the respondent does not receive the question about partners in the past 12 months, the data will be coded as missing for this variable. Analysts may want to recode this to “0.”

For questions that ascertain total number of partners for all types of sex (i.e., SXD171, SXD510, SXD101 and SXD450), if the respondent had reported never having any type of sex, the responses were coded as “0.”

Although the ACASI has many advantages over interviewer-administered questionnaires for sensitive information, inconsistent responses can occur. Since the questionnaire is self-administered, unlikely answers or confusing questions cannot be clarified by the interviewer. Although, the questionnaire was programmed to alert respondents of potential data entry errors or inconsistencies, not every possible consistency check was added. To minimize potential respondent frustration and confusion, the interview was not interrupted each time an inconsistent answer occurred in terms of the number of sexual partners for different periods of recall for different types of sexual behavior.

Exam sample weights should be used for analyses. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.